The objective of this study is to determine the influence of xenobiotic exposure on the capability of human placental tissues to transform proteratogens into reactive toxic metabolites (teratogens) harmful to developing embryos. In this study, human placental tissues from individuals who smoke cigarettes will be utilized to test the hypothesis that such exposure augments the potential of placental tissues to produce reactive-teratogens from model polynuclear aromatic hydrocarbon (PAH) substrates (e.g., benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene). Benzo[a]pyrene hydroxylase (Aryl hydrocarbon hydroxylase) and other mixed function oxidase (MFO) enzyme activities are to be measured in human placental tissues of first trimester legal abortions and also of term pregnancies, to survey the patterns of development of MFO enzymes in these tissues of smoker and non-smoker donors. The augmentation possibilities of MFO enzymes by specific PAHs in in vitro cultures of intact chorionic villi or isolated and purified trophoblast cells will also be studied. The potential for producing toxic-reactive or non-toxic metabolites by placental tissues and trophoblast cells from PAH-proteratogens will be assessed by in vitro incubation of these tissues and cells with PAH, and by analysis of the metabolites produced. Biochemical procedures of liquid and gas chromatography and mass spectrometric determination, binding of reactive metabolites to exogenous DNA, and biological assay of mutagens by Salmonella/microsome test systems are to be used for these analyses. To elucidate toxic potential of PAH metabolites on embryogenesis, rat/mouse conceptuses of pregnancy days 10 and 11 during embryonic organogenesis will be, cultured in vitro by an improved procedure, with human placental microsomes having toxic metabolism potential and PAH. Conceptus cultures are also to be performed with original and possible reactive metabolites microinjected into different conceptus compartments. In vitro embryogenesis will be monitored for the toxic effects of PAH by dysmorphic organ development, covalent binding of PAH with DNA, and aberrant oncogene expression in embryonic tissues. These experiments will permit evaluation of the impact of a xenobiotic contaminated environment on toxic metabolism potential of human placental tissues and the nature of injuries such metabolites may produce in developing embryos.